From The Collaborative International Dictionary of English v.0.48 [gcide]: Spiral \Spi"ral\, n. [Cf. F. spirale. See Spiral, a.] 1. (Geom.) A plane curve, not reentrant, described by a point, called the generatrix, moving along a straight line according to a mathematical law, while the line is revolving about a fixed point called the pole. Cf. Helix. [1913 Webster] 2. Anything which has a spiral form, as a spiral shell. [1913 Webster] Equiangular spiral,a plane curve which cuts all its generatrices at the same angle. Same as {Logarithmic spiral}, under Logarithmic. Spiral of Archimedes, a spiral the law of which is that the generatrix moves uniformly along the revolving line, which also moves uniformly. [1913 Webster]